1. Field of the Invention
The present invention relates to a metallic double-sided element for a slide fastener, having a coupling convex portion and a coupling concave portion on both front and rear surfaces thereof.
2. Description of the Related Art
Slide fasteners have been widely used in an opening of bags or the like in order to open/close the bags or the like. As one of such slide fasteners, there is known a slide fastener in which two sliders are arranged on a fastener chain such that their heads oppose each other or their bottoms oppose each other, whereby the fastener chain can be opened/closed even when the slider is slid in any direction of forward and backward along element rows.
Double-sided elements are used in the slide fastener having the two sliders. Such a double-sided element is configured such that a coupling head thereof is formed into a symmetrical shape in regard to its front face and rear face (back to forth in a sliding direction) in order to provide operating feeling of the slider in each direction with no difference when the slider is slid forward or backward with respect to the element row. Particularly, the metallic double-sided element having excellent strength, appearance, durability and flexibility, etc. is used in the opening of clothes, bags and the like using strong fabric.
Examples of the double-sided elements have been disclosed in Japanese Utility Model Application Laid-Open No. 1-80012 (patent document 1), Chinese Utility Model Application Publication No. 2170665Y (patent document 2) and the like. A double-sided element 51 described in the patent document 1 as shown in FIG. 10 includes a coupling head 52, a body portion 53 disposed at the rear end side of the coupling head 52, and a pair of right and left leg portions 54a, 54b extending to the rear end side of the body portion 53.
The coupling head 52 includes a flat plate portion 52a thinner than the body portion 53, coupling convex portions 52b projecting from front and rear faces of the flat plate portion 52a, right and left projecting edge portions 52c disposed on both right and left side edges of the element 51 and projecting forward from the body portion 53, and a coupling concave portion 52d formed between the coupling convex portion 52b and the body portion 53. In the double-sided element 51 of the patent document 1, improvement of its coupling strength is achieved by forming the coupling convex portions 52b higher than the flat plate portion 52a when the element 51 is molded by pressing.
In this case, to provide the coupling convex portion 52b projectingly high in a predetermined shape, it is necessary to use the thickness around the coupling convex portion 52b. For the purpose, the right and left projecting edge portions 52c disposed on the coupling head 52 are formed with their projecting length from the body portion 53 limited, and the coupling convex portion 52b and the right and left projecting edge portions 52c are disposed apart from each other. Further, the height of the bottom face of the coupling concave portion 52d is set to the same one as the front and rear faces of the flat plate portion 52a, and the flat plate portion 52a is provided at the front end side of the coupling convex portion 52b.
According to the patent document 1, a front end face 52e of the flat plate portion 52a is formed wide and flat in the right-left direction. Thus, by constructing the slide fastener using the double-sided element 51 of the patent document 1, a chain width when the elements are coupled can be reduced so as to obtain a slide fastener having an excellent appearance.
On the other hand, the double-sided element 61 described in the patent document 2 as shown in FIGS. 11 and 12 includes a coupling head 62, a body portion 63, and a pair of right and left leg portion elements 64a, 64b, as shown in FIGS. 8 and 9. The coupling head 62 has a flat plate portion 62a formed thinly, a slope portion 62b disposed between the flat plate portion 62a and the body portion 63, and central convex portions 62c and right and left convex portions 62d projecting from the front and rear surfaces of the flat plate portion 62a.
The central convex portion 62c is disposed in the center in the right-left direction of the front end side of the flat plate portion 62a. Each side face of the front, rear, right and left sides is formed of an inclined face such that the bottom portion is expanded. The right and left convex portion 62d is disposed inside of right and left side edges of the element 61 and between the central convex portion 62c and the slope portion 62b while its peripheral face is formed in a tapered configuration. Particularly, the right and left convex portions 62d are constructed so that the edge on the front end side makes linear contact with the edge of the central convex portion 62c while its rear end is invading into the slope portion 62b.
In the double-sided element 61 of the patent document 2, a coupling concave portion 62e is formed among the central convex portion 62c, the right and left convex portions 62d and the slope portion 62b. Further, the height in the front surface-rear surface direction of each of the right and left convex portions 62d is set larger than the body portion 63, and the height in the front surface-rear surface direction of the central convex portion 62c is set larger than each of the right and left convex portions 62d. Because in the slide fastener constructed with the double-sided element 61 of the patent document 2, the heights of the central convex portion 62c and the right and left convex portions 62d are set higher than the body portion 63, the right and left elements 61 can be securely coupled with each other.
In the double-sided element 51 for the slide fastener described in the patent document 1 (see FIG. 7 10), the coupling convex portion 52b is provided projectingly on the front and rear surfaces of the flat plate portion 52 independently of the body portion 53 and the right and left projecting edge portions 52c. Assume that the slide fastener is constructed using the double-sided element 51 of the patent document 1. In this case, if the fastener element 51 receives an external force such as a lateral pulling force when the elements 51 are in coupling, the independent coupling convex portion 52b is likely to be deformed or chipped by its stress. In addition, the coupling convex portion 52b is hooked easily between the coupling convex portion 52b and the projecting edge portion 52c of a mating element, thereby providing a possibility that coupling strength may drop.
When the double-sided element 51 of this patent document 1 is attached to the fastener tape, the fastener tape is inserted in between the right and left leg portions 54a and 54b with the right and left leg portions 54a, 54b opened at a predetermined angle, and then the leg portions 54a, 54b are caulked inward, so that the elements are implanted successively at a predetermined pitch onto the element attaching portion of the fastener tape. However, when the right and left leg portions 54a, 54b of the element 51 are caulked in this way, the right and left leg portions 54a, 54b are deformed plastically to hold the fastener tape and at the same time, the coupling head 52 of the element 51, particularly, the right and left projecting edge portions 52c are deformed so that they are expanded outward. Consequently, there is a fear that the coupling state, coupling strength and the like of the element 51 might be affected when the slide fastener is constructed.
Further, because the double-sided element 51 of the patent document 1 is provided with the flat plate portion 52a formed on the front end side of the coupling convex portion 52b, sliding resistance is large when the slide fastener is opened or closed, whereby operation feeling of the slider is heavy. Additionally, the flat plate portion 52a may be formed on the front end side of the coupling convex portion 52b. In this case, for example, when a user touches an element row, he or she likely feels that the flat plate portion 52a is projected from the coupling head 52 and thus, there is a room for improvement in the tactile feeling and the like on the element rows.
On the other hand, the double-sided element 61 for the slide fastener described in the patent document 2 is so constructed that the central convex portion 62c and the right and left convex portions 62d keep contact through their edges, the peripheral wall of the coupling concave portion 62e is not formed continuously so that it is interrupted between the central convex portion 62c and the right and left convex portions 62d. Thus, the central convex portion 62c and the right and left convex portions 62d are not formed so as to support each other but the central convex portion 62c and the right and left convex portions 62d are provided substantially independently.
For this reason, the element 61 of the patent document 2 has such a problem that when a slide fastener is constructed with the elements, the central convex portion 62c is likely to be deformed or chipped thereby deteriorating its coupling strength, when the element receives a lateral pulling force or the like upon coupling of the elements 61 like the case of the patent document 1. Further, in the double-sided element 61 of the patent document 2, when the right and left leg portions 64a, 64b are caulked to attach the element to the fastener tape, the right and left convex portions 62d and the flat plate portion 62a disposed outside thereof are likely to be deformed such that they are expanded outward, like the case of the patent document 1.
Further, in the double-sided element 61 of the patent document 2, the flat plate portion 62a is disposed on the front end side of the central convex portion 62c also. Thus, when the slide fastener constructed with the double-sided elements 61 is opened or closed, a large sliding resistance is applied to the slider so that the operation feeling of the slider becomes heavy, thereby worsening the tactile feeling of the element rows, which is a disadvantage.